1. Field of the Invention
My present invention comprises a friction pivot point, of a type particularly suitable for use as a friction pivot joint in a window stay.
2. Description of Related Art
Such friction pivot joints as are described in, for example, New Zealand patent specification Nos. 144922/146130/146886, 162919, 196479 are typically employed to frictionally movably couple two arms of a window stay, or an arm of a stay and a frame or sash plate, and comprise a rivet which extends through two apertures formed one in each of the adjacent ends of the arms to be joined and a bushing formed of a self-lubricating material such as nylon or suitable plastics material, interposed therebetween to prevent metal to metal contact in the joint between moving parts of the arms and rivet. When such joints are provided in window stays it is important that the joint be accurately formed and the rivet, which holds the joint together and applies the friction providing pressure thereto, properly centered. If the rivet is off-centre and/or `leaned` to one side during manufacture for example, the joint will be inaccurately formed and the arms will not extend in the same plane. Any misalignment at the joint is magnified at the distal ends of the arms and thus it is important that such joints are so constructed as to minimize such difficulties.
An improved form of such a friction pivot joint is described in my New Zealand patent specification No. 202214/202755 wherein the joining rivet is eliminated.
Reference is also made to U.S. Pat. No. 4,582,435 which is based on the New Zealand patent specification Nos. 202,214 and 292,755. Instead, arm material is extruded from the end of one arm through an aperture formed in the end of the other arm so that a `turret` of arm material is provided at the end of the first arm, which turret extends through the aperture in the other arm. In the formed joint a self-lubricating bushing is interposed between the turret of the one arm and the other arm and the turret is crimped down to form a permanent joint. This form of bearing is conveniently referred to as an integral bearing. In order that sufficient material is present in the arm in which the turret is formed, to enable the turret to be formed therein, it is necessary that this arm at least be of a substantial thickness and this, rather than the strength of the arm required, is a limiting factor on the thickness of the arm provided. It is typically necessary to provide a significantly thicker arm than would otherwise be required simply to provide the required strength alone.